For golfers, flight distance of a ball is one of the important factors when selecting a golf club. Therefore, hitherto, in order to extend the flight distance of the ball, various improvements have been made with regard to shapes and materials of elements forming a golf club.
For example, when the weight of a head is large, kinetic energy provided to a ball when the ball is hit becomes large and the speed of the ball can be increased, and, as a result, a large flight distance can be obtained. Therefore, a technique for increasing a head weight by increasing the proportion of the head weight with respect to the total weight of a golf club has been proposed (e.g., see Patent Literature 1).